MSVC: Factor out enable_language(RC) call into helper macro

This will be useful to call from elsewhere later.

Modules/Platform/Windows-MSVC.cmake

@@ -366,12 +366,15 @@ macro(__windows_compiler_msvc lang)
   endif()
   set(CMAKE_${lang}_LINKER_SUPPORTS_PDB ON)
   set(CMAKE_NINJA_DEPTYPE_${lang} msvc)
+  __windows_compiler_msvc_enable_rc("${_PLATFORM_DEFINES} ${_PLATFORM_DEFINES_${lang}}")
+endmacro()
 
+macro(__windows_compiler_msvc_enable_rc flags)
   if(NOT CMAKE_RC_COMPILER_INIT)
     set(CMAKE_RC_COMPILER_INIT rc)
   endif()
   if(NOT CMAKE_RC_FLAGS_INIT)
-    string(APPEND CMAKE_RC_FLAGS_INIT " ${_PLATFORM_DEFINES} ${_PLATFORM_DEFINES_${lang}}")
+    string(APPEND CMAKE_RC_FLAGS_INIT " ${flags}")
   endif()
   if(NOT CMAKE_RC_FLAGS_DEBUG_INIT)
     string(APPEND CMAKE_RC_FLAGS_DEBUG_INIT " /D_DEBUG")